Btw, I think the GPIO speed setting was set to "MEDIUM" due to Pito's recommendation for F4 SDIO to work.
Well, SDIO works for libmaple F4 with GPIO set to push-pull with enabled pull-up and the default push-pull speed "HIGH" (50MHz).

It does work with MapleMini and the latest, connected via COM4 STM32 Virtual port. I do not have BP handy today.
It does work with Black F407ZET and the latest, connected via COM4 STM32 Virtual port.
There is the USBSerial TX issue, however (82x slower than normal).

The Blue F103ZET and the latest - I get a bubble message "USB device not recognized" when inserted the USB, with "Unknown device" in the DevMan, none yellow triangle in the DevMan.

The -DARDUINO_ARCH flag - I think it is a bad idea to derive the architecture name based on the repo folder's name..
I will hard-wire it ARDUINO_ARCH_STM32 here in my platform.txt, as I am using 8 folders for various repos (and their different versions) here.
And Roger has in his libmaple the folders called STM32F1, STM32F3, STM32F4 in there - and the arch is ARDUINO_ARCH_STM32 (at least SdFat is using that flag).
Moreover, everything in stm32duino is _STM32 architecture..